The most common and most likely answer to this crossword clue is the 6 plus 4 letter word MAGNUM OPUS
I've seen this crossword clue in The Guardian
M
A
G
N
U
M
O
P
U
S
More clues leading to the result MAGNUM OPUS
- Publication by students with classy, clean content, fantastic achievement
- Great achievement having bottle back to drink nothing
- Very large sandwiches turned up with plenty of bubbly — terrific work!
- Bottle with boiling soup – great work!
- Sorcerer’s inspired upon newly embracing Mahler’s first great work
- Large wine bottle and spilt soup presented as a great work of art
- Bubbly soup needs work, significant work
- Arts graduate mugs up on new work rated very highly
- Much champagne pours out without hint of restraint: great work!
- The old lady mugs up on remarkable person’s greatest work
Buddy explains!
The straight part
We know that "great work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case great work = magnum opus.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.